This invention relates to biopsy needles and more particularly relates to needles that can cut a tissue sample internally within a patient and then withdraw the sample.
A number of biopsy needles for taking tissue samples are known but unfortunately such known needles have one or more serious disadvantages. Many of such needles, e.g. as described in U.S. Pat. Nos. 4,640,296; 5,040,542; 5,492,130; 5,843,023; 5,916,175; European Application 0 455 626; British Application 2 347 862 and International Application WO 00/56220 rely upon an open cutting edge of the needle which cuts around a sample and forces it into the needle. With such a configuration, the end of the sample is not severed but the operator must move the needle within the patient to finally tear the end of the sample from attached tissue. Such a procedure in a conscious patient can be extremely painful and traumatic and in any case can cause significant tissue damage to areas surrounding the removed sample. This unsatisfactory procedure is clearly illustrated in British patent application 2 347 862.
Another set of known biopsy needles does not cut at the tip of the needle but instead relies upon tissue overflowing into a side opening which is then cut off by a sliding sheath or other cutting means. Such needles are for example described in U.S. Pat. Nos. 4,600,014; 5,224,488; 5,313,958; 5,507,298; and 5,611,352. While such needles are an improvement in that the entire sample is cut rather than partially torn from a patient, there is another different problem associated with such needles. In particular, such needles rely upon tissue overflow into the side opening. The samples, if present at all, are thus irregular.
At least one attempt has been made to cut an entire sample while using an opening at the tip of the needle. Such an attempt is described in U.S. Patent No. 4,651,752. Unfortunately, the needle structure of U.S. Pat. No. 4,651,752 is complex with rough sides that can tear and bruise tissue and further would be very difficult to make in a small needle.